Centrifugal casting apparatus



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into the mold cavity in the rotary mold- Patented July 14, 1925.

UNITED STATES.

JEAN H. L. DE BATS, OF WHITMAN, MASSACHUSETTS.

CENTRIFUGAL CASTING APPARATUS.

Application filed December 13, 1922. Serial No. 606,617.

To all whom it may concern;

Be it known that I, J RAN H. L. DE BATS, a subject of the Queen of, the Netherlands. and resident of Whitman, county of Plymouth, State of Massachusetts, have invented an Improvement in Centrifugal Casting Apparatus, of which the following description, in connection with the accompanying drawing, is a specification, like characters on the drawing representing like parts.

This invention relates to casting apparatus of the centrifugal type and it has for one of its objects to provide a novel casting apparatus of this type which is constructed so as to facilitate the flow of metal through the gate into the mold cavity. This object is accomplished by providing a stationary gate through which the metal is introduced member, the provision of such stationary gate developing a suction at the delivery end thereof which facilitates the flow of the metal into the mold cavity.

Another object of my invention is to pro- .vide a novel centrifugal casting apparatus by which saws and other relatively thin disk-like articles canbe successfully cast.

An advantage which is inherent in the centrifugal process of casting wherein the molten metal is poured into a rotating mold, is that the centrifugal force developed by the rotation of the mold insures that the metal will be carried clear to the periphery ofthe mold and also holds it under compression until it is cooled.

A disadvantage, however, which sometimes arises when this method of casting is used for casting cutting tools is that internal strains are apt to develop in the article while the metal is cooling, such strains beingsometimes sufiicient so as to cause the article to break readily when it is put in use. Such internal strains are developed during the shrinkage which the metal undergoes while it is cooling. When the metal shrinks as it cools there is a tendencyfor the shrinkage to occur equally in all parts and for the metal to draw inwardly slightly from the periphery of the mold. If, for instance, the metal should adhere to the periphery of the mold at some point, then during such shrinkage an internal strain would be set up which might result in a fracture of the tool as soon as it is put in use.

One of the objects of my invention is to provide a centrifugal casting ap aratus adapted to cast saws or other thin 'sks so that they will be free from internal strains, and yet will have all the advantages due to casting the metal by the centrifugal process.

I secure this end by providing a rotary mold having a peripheral portion which is yieldable inwardly but is held against outward expansion. The-advantage of the mold with such a yieldable peripheral portion is that if the metal should adhere to any rtion of the peripheral wall of the mold w ile the metal is shrinking such portion of the wall may yield inwardly as the metal shrinks so as to obviate the formation of any internal strain in the casting.

In order to give an understanding of the invent-ion I have illustrated in the drawings a selected embodiment thereof which will now be described after which the novel features will be pointed out in the appended claim.

Fig. 1 is a vertical sectional view illustrating an apparatus embodying my invention;

Fig. 2 is a plan View of the mold with the upper portion removed;

'Fig. 3 is a perspective view of a-saw which is cast in my improved mold.

The apparatus herein shown comprises a rotary mold member 1 having a mold cavity 2 which is' herein shown as having a shape adapted to cast a thin disk such as the saw 3 illustrated in Fig. 3. For casting this saw the mold cavity will have a. serrated peripheral portion as shown at 4:. The mold member may be rotated in any suitable way and I have herein shown it as carried by the shaft 5 of a high-speed motor 6.

The upper side of the mold cavity 2 is closed by a block 7 having a gate 11 rovided with a central opening 8 thatlea s to the mold cavity and through which the molten metal is poured into the cavity. .The mold member 1 is shown as having a central post or hub 9 which rises into the opening 8 and which forms the central opening 10 of the saw 3. This st 8 as well as the gate 11 .may "convenientlybe made of carbon.

The casting is performed as usual in centrifugal castlng machines by rotating the ion iUS

mold member 1 and then pouring the molten metal through the opening 8 of the gate 11.

stationary so that the molten metal is delivered into the rotating mold cavity In the present invention the gate 11 is 1 block 7 rotates with the mold member then through the stationary gate. The result of this'operation is that a suction will be produced at the lower end of the gate which will assist in drawing the metal through the gate into the mold cavity, thus facilitat ing the delivery of the molten metal to saidmoldcavity and there is no tendency for the metal to be thrown outwardly from the gate as would occur if the gate itself were rotating with the mold member. This feature of the stationary gate and rotary mold member may be provided for either by making the cap block or member 7 stationary with the gate or by having said cap block 7 rotate with the mold member while maintaining the gate 11 stationary. If the block 7 is stationary then the contactin surfaces of the rotary mold member and block will be lubricated with a bite or some other lubricant to reduce friction, while if the the contacting faces of. the block and gate 11 will be-similarly lubricatedJ. 3

The gate 11 may be held from rotation in any suitable way as by means of a member 15 which is fixed to some suitable frame and is connected to the gate. If the member 7 is held stationary any similar device may be used for preventing it from rotation.

The stationary gate obviates any tendency for the metal which is poured through theopcning 8 to be thrown upwardly from the mouth of the opening as is apt to occur if the gate rotates. Moreover the use of the stationary gate develops a suction at the delivery end thereof which draws the metal into the mold cavity.

As stated above my invention also includes a mold member in which the mold cavity has a yieldable peripheral portion so that if the metal adheres to said peripheral portion at any point while it is coolingand shrinking such portion of the periphery may yield inwardly suficiently to accommodate the shrinkage and thereby prevent the formation of internal strains in the cast article. This yieldable peripheral portion of the mold may be provided for in various ways without departing from the invention.

One construction is herein illustrated wherein said portion of the mold is formed of a plurality of separate radially-arranged blocks or sections 12. The circumferential width and the number of such blocks or sec tions may vary without departing from the invention. \Vhere the article being cast is in the nature of a saw with teeth 13 it may be convenient to have as many blocks or sections 12 as there are teeth, the inner end of each block shaped to form one of the teeth 13 of the article 3. These blocks are all backed by an enclosing wall 14 which um mally holds then in position and prevents them from expanding or moving outwardly. The blocks fit each other closely enough so that during the'castin'g operation no metal will work into the joint between adjacent blocks but because the blocks are separate from each other each block is permitted to give or move slightlyinwardly in a radial direction. In other words it is possible to have the blocks fit each other well enough so that no metal will be forced into the joint between the blocks by centrifugal action while at the same time having the blocks spaced far enough so that each block will hepermitted to move inwardly a distancecorresponding to the amount which the metal will shrink. V

With this arrangement the peripheral portion of the mold. cavity is not yieldable as regards outward movement so that a perfect casting can be produced while at the same time it is yieldable in an inward direction to -an extent corresponding-to the amount of shrinkage in the metal. It, therefore, the metal of the casting should adhere to the peripheraliportion at any point then when the shrinkage of the metal occurs the block or blocks to which the metal adheres can move inwardly as the metal shrinks and thus prevent the formation of' any internal strains in-the metal. This makes it possible to east very thin diskl ike articles such as the saw shown in Fig. 3 because the centrifugal force developed by the rotation of the mold ensures that the metal will flow to all parts of the peripheral portion of the mold and a solid casting will be made while at the same time the development of any internal strains is avoided due to the inwardly-yielding peripheral portion of the mold cavity.

While I have herein illustrated one rm]- st-ruct'ion by which internal strains in the casting may be avoided yet I do not wish to be limited to the constructional features shown.

I claim: In a centrifugal casting apparatus, a rotary mold member llflVlIl" a recess in its upper face and a peripher l wall surrounding the recess, a plurality of separate blocks arranged in abutting relation and engaging said peripheral wall, and a stationary gate member situated above the. rotary member and forming therewith a mold cavity, the periphery of which is formed by the inner edges of the blocks, 'said peripheral walls preventing said walls from outward movement but permitting them to hav a slight inward movement.

In testimony whereof, I have signed my name to this specification.

. H. L. DE BATS. 

